1. Field of the Invention
The present invention relates to photographic apparatus and more particularly to apparatus for controlling focus and exposure in an automatic camera.
2. Discussion Related to the Problems
Automatic cameras are known which feature both automatic focus and automatic exposure control. Typically, in such an automatic camera, an electronic control circuit responsive to signals produced by input transducers (usually photoelectrical devices such as photocells) produces electrical control signals for controlling the camera mechanism by means of electromechanical output transducers. An output transducer is required for each camera function which is independently controlled. A very popular type of output transducer is the servo motor. However, as the number of automatically controlled camera functions increases to include, for example, focus, aperture size, film winding and shutter cocking, the corresponding proliferation of servo motors results in bulky and expensive apparatus. A goal, therefore, has been to minimize the number of such motors in the camera. An example of an automatic camera wherein one motor controls focus, advances film and cocks the shutter is shown in U.S. Pat. No. 3,917,395 issued to Ogawa on Nov. 4, 1975, and entitled CONTROL CIRCUIT FOR PHOTOGRAPHIC APPARATUS.
In the apparatus shown by Ogawa, however, the aperture size cannot be controlled independently of the exposure time. The relation between aperture size and shutter time is determined by the mechanical design of the shutter. Commonly assigned and copending U.S. Patent Application Ser. No. 103,260 entitled METHOD AND APPARATUS FOR AUTOMATIC CONTROL OF A PHOTOGRAPHIC CAMERA by Schauffele et al, filed on the same day as the present application, discloses a technique and apparatus for determining the optimum settings in a camera having an adjustable lens and adjustable aperture size and shutter time. In an automatic camera employing this technique, the aperture size and shutter time must be independently controllable. The problem faced by the present inventor was to provide a control mechanism in which all these adjustments are made automatically and mechanically independently of each other while minimizing the use of servo motors and the complexity of the apparatus.